Conventional ice cream and related products contain a substantial amount of fat (generally 8-14% by weight). Furthermore, they generally contain proteins (3-8%) and sugars (12-20%). Fat is herein to be understood to mean triglycerides. Minor ingredients generally present are stabilizers, emulsifiers, flavours and colorants. Such a conventional ice cream product has large calorific value mainly due to the presence of fat and sugars.
Fat plays an important role in ice cream. It is generally known to the man skilled in the art that fat droplets or globules (partially coated with emulsifiers and proteins) are of prime importance for the stability and structure of ice cream. This structure can be considered to comprise air bubbles fixed in a matrix of solids and partially frozen liquids and emulsions. It is preferred for a good structure and stability that a part of said fat droplets are agglomerated or destabilized. These agglomerates are formed during processing of the ice cream emulsion. The destabilization of the fat droplets is a very critical process, depending on e.g. process conditions and amount and type of fat, proteins and emulsifiers used. The chances of getting too much agglomeration (resulting in an oily oral sensation upon eating) or no agglomeration at all (resulting in a poor structure of the ice cream) are considerable. Not only the structure of the ice cream is determined by the agglomeration, but also the melting behaviour is strongly influenced by it. It is desired that ice cream does not melt away too quickly, but it is also desired that melting does occur when the ice cream is exposed to elevated temperatures, otherwise the product will result in a mousse, which is a different product. Therefore, it is desired that ice cream exhibits a gradual or controlled melting behaviour when exposed to elevated temperatures, especially in the mouth upon eating. Melting behaviour of ice cream and related products can suitably be determined by using a standard melting test as disclosed by Arbuckle in "Ice Cream", The Avi Publishing Co. 4th edition page 364 (1986).
As stated above, among the factors having an influence on the agglomeration of fat droplets are fat and its interaction with emulsifiers. Although there are a number of suitable food grade emulsifiers, fatty acid monoglyceride esters (for short: monoglycerides) are commonly used. There is, however, a specific class of monoglyceride emulsifiers which, when present to a certain extent, enhances the agglomeration or destabilization of fat and thereby influences the melting behaviour of the ice cream. Said specific emulsifiers are monoglycerides of unsaturated fatty acids, or for short: unsaturated monoglycerides.
The degree of saturation of fatty acids and derivatives thereof like mono- and diglyceride esters is normally quantified by the iodine value (IV). It is common practice to regard fatty acids or derivatives thereof having an IV of larger than 3 as being at least partly unsaturated. Partly is herein to be understood as a mixture of saturated and (mono- or poly-) unsaturated fatty acids or derivatives thereof.
The effect of unsaturated fatty acid monoglycerides on the emulsifying of fat in ice cream and its subsequent effect on fat agglomeration and thus on the melting behaviour and related organoleptic properties is discussed in a number of references, e.g. by J. J. Kloser and P. G. Keeney in "The ice cream journal" of May 1959 (page 26-121), by K. Sistrup in S usswaren, 14, 695-699 (1970), by H. Amano et al. in U.S. Pat. No. 4,127,679 (1978), by Y. K. Cho in the Korean J. Food Sci. Technol. 20(2) 236-241 (1988), by H. D. Goff and K. Jordan in J. of Dairy Sci. 72, 18-29 (1989) and by N. M. Barford et al. in Fat Sci. Technol. 93(1), 24-29 (1991). All these references relate to ice cream having a substantial amount of fat.
Since the beginning of the 1980s, there is an increasing demand for confectionary products and desserts, including ice cream and related products, having a reduced calorific value. A common way of achieving this is by reducing the amount of fats and/or carbohydrates present and/or by replacement of these compounds with materials resembling the properties of fat or carbohydrates, but not having the same amount of calories. Reducing the amount of fat present in ice cream is a most effective way for reducing the calorific value, since fat has a calorific value per gram which is more than twice as high as the value for carbohydrates. The amount of fat present in ice cream may be lowered to about 3 to 5% while it is still able to perform it stabilizing action on the aerated mix and thus maintaining acceptable melting properties. By reducing the amount of fat in ice cream, further, however, considerable difficulties arise, because fat cannot play its important role in connection to structure and melting behaviour, as is described above. These difficulties rise to enormous problems when substantially all fat is omitted from ice cream, which is the object when producing an ice cream like product having a reduced amount of calories. Such a product can better be described as a zero fat whipped frozen dessert product.
This means that a considerable problem is encountered when trying to make a zero-fat whipped frozen dessert having a controlled melting behaviour when exposed to elevated temperatures.
One way of solving this problem is by using a fat-simulating material having zero calories. Such a solution is disclosed by Whelan et al. in the patent application published as WO 91/11109. Herein it is shown that polyol fatty acid polyesters having at least 4 fatty acid ester groups can replace fat (i.e. triglycerides) in conventional ice cream and thus maintaining good organoleptic properties. Use of such a material, however, has the considerable disadvantage of having either an undesirable laxative effect or giving a waxy feeling in the mouth.
In U.S. Pat. No. 4,400,405 by Morley et al. zero-fat whipped frozen dessert products for soft serve purposes at home freezer temperatures are disclosed. This is achieved by using specific sugars and related compounds which are known to have a softening effect on ice cream, such as dextrose, fructose, glycerol, sorbitol and high fructose syrups. Emulsifiers used for the products according to the reference are mono- and diglycerides. The only mono- and diglycerides which are specified have saturated fatty acid chains. The product according to the reference does not exhibit controlled melting behaviour.